Noise and Environment
Edited by Daniela Siano and Alice Elizabeth González Edited by Daniela Siano and Alice Elizabeth González
Noise pollution is one of the factors that affect the quality of life of the general population, especially in urban areas, where the noise levels are often high due to the presence of numerous sources, such as transport infrastructures, activities production and commercial
areas, entertainment venues and other sound sources which, although temporary, such as construction sites and outdoor music events, affect general noise levels. Even if noise is one of
the oldest pollutants referred to in history, for years, the problem of noise pollution has been often considered less important than others related to the environment, such as air pollution,
water pollution, and waste management.The regulations in force to contain the noise have become increasingly stringent as each individual is constantly exposed to noise and often the noise is treated just as a scourge of modern society. Making noise is becoming easier and cheaper each day, but just the opposite for controlling it. Deeper studies are needed to understand the core of current noise problems; new materials and techniques are needed to control them. This book is a combination of theory and practice based on the latest research.
The studies in this book range from evaluation methods for the perception of noise and outline forecast criteria that can be integrated with applications for acoustic mapping as well as the use of innovative techniques and materials for its abatement. The main purpose of this book, organized in 8 chapters, is to provide an overview of the recent studies in this field and the applications in different research studies. The authors, contributing to the success of this book, provide a series of practical applications of their recent studies aimed at the reduction
of noise in different environments. The editors would like to thank all the authors who, through their studies and research, have accepted our invitation to share recent discoveries
in this field with the scientific community.
Published in London, UK
© 2021 IntechOpen
© goir / iStock
ISBN 978-1-83968-239-1
Noise and Environment
Noise and Environment
Edited by Daniela Siano and Alice Elizabeth González
Published in London, United Kingdom
Supporting open minds since 2005
Noise and Environment
http://dx.doi.org/10.5772/intechopen.87872 Edited by Daniela Siano and Alice Elizabeth González Contributors
Juan Rios, Celedonio Aguilar, Jānis Indulis Dundurs, Inka Janna Janssen, Mia Suhanek, Sanja Grubesa, Vijaya Baskar Veeriayan, Rajendran V, Jiho Lee, Himanshu Dehra, Mohamed Abdelsabour Abdelsabour Fahmy
© The Editor(s) and the Author(s) 2021
The rights of the editor(s) and the author(s) have been asserted in accordance with the Copyright, Designs and Patents Act 1988. All rights to the book as a whole are reserved by INTECHOPEN LIMITED.
The book as a whole (compilation) cannot be reproduced, distributed or used for commercial or non-commercial purposes without INTECHOPEN LIMITED’s written permission. Enquiries concerning the use of the book should be directed to INTECHOPEN LIMITED rights and permissions department ([email protected]).
Violations are liable to prosecution under the governing Copyright Law.
Individual chapters of this publication are distributed under the terms of the Creative Commons Attribution 3.0 Unported License which permits commercial use, distribution and reproduction of the individual chapters, provided the original author(s) and source publication are appropriately acknowledged. If so indicated, certain images may not be included under the Creative Commons license. In such cases users will need to obtain permission from the license holder to reproduce the material. More details and guidelines concerning content reuse and adaptation can be found at http://www.intechopen.com/copyright-policy.html.
Notice
Statements and opinions expressed in the chapters are these of the individual contributors and not necessarily those of the editors or publisher. No responsibility is accepted for the accuracy of information contained in the published chapters. The publisher assumes no responsibility for any damage or injury to persons or property arising out of the use of any materials, instructions, methods or ideas contained in the book.
First published in London, United Kingdom, 2021 by IntechOpen
IntechOpen is the global imprint of INTECHOPEN LIMITED, registered in England and Wales, registration number: 11086078, 5 Princes Gate Court, London, SW7 2QJ, United Kingdom Printed in Croatia
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library Additional hard and PDF copies can be obtained from [email protected] Noise and Environment
Edited by Daniela Siano and Alice Elizabeth González p. cm.
Print ISBN 978-1-83968-239-1 Online ISBN 978-1-83968-240-7
Selection of our books indexed in the Book Citation Index in Web of Science™ Core Collection (BKCI)
Interested in publishing with us?
Contact [email protected]
Numbers displayed above are based on latest data collected.
For more information visit www.intechopen.com
5,200+
Open access books available
Countries delivered to
156 12.2%
Contributors from top 500 universities Our authors are among the
Top 1%
most cited scientists
127,000+
International authors and editors
150M+
Downloads
We are IntechOpen,
the world’s leading publisher of Open Access books
Built by scientists, for scientists
CITATIONBOOK INDEX
CLARIVATE ANALY TICS
IN D E XE D
Meet the editors
Daniela Siano was born in Naples - Italy, and graduated in Aero- nautical Engineering from the University of Naples “Federico II”, Italy in 1994. Until 2001, she was a researcher in the Acoustic and Vibration Department at C.I.R.A. (Italian Aerospace Re- search Center). From 2001 until now, she has been a researcher at the National Research Council of Italy (CNR) in the field of acoustic and vibration in the transport field. She is responsible for the Acoustic and Vibration Laboratory. She is qualified to University Associate Professor – Sector Machines and Systems for Energy and Environment, and is also qualified in the Engineer Profession. She had a scholarship granted by M.A.R.S.- Microgravity Advanced Research and Support - Dornier GmbH (Friedrichshafen - Germany), Euromaster in “Total Quality Management” at DIMP – Department of Mechanical and Production Engineering – University of Naples Federico II – Italy, as well as assistant in “Fluid Machines I”, “Fluid Machines II”, and “Applied Mechan- ics”. She is the tutor of more than 30 Master’s students and 7 Ph.D. students. She is an expert evaluator within the EU 6th and 7th Framework Research Programme, in Transport-Aeronautics in 2006 and 2007. She is a project expert evaluator in the Ministry of Economic Development, Italy. She is a referee for different inter- national journals and session organizers collaborating with SAE conferences. She is the author of more than 100 scientific papers published in international journals and conferences proceedings and editor of two scientific books: ‘Noise Control, Reduction and Cancellation Solutions in Engineering’, ISBN 978-953-307-918-9, 308 pages, DOI: 10.5772/1375, and ‘Fuel Injection’, ISBN 978-953-307-116-9, 262 pages, DOI: 10.5772/55402.
Alice Elizabeth González is a full-time Professor at the Envi- ronmental Engineering Department, Faculty of Engineering, Universidad de la República (UdelaR, Uruguay). She currently teaches undergraduate and postgraduate programs and oversees graduate and postgraduate students. She also leads research, development, and applied research projects. She is a Researcher of the National Researchers System of the National Research and Innovation Agency. Her main research topic is noise pollution, including environ- mental and urban acoustics, noise and vibration control, environment and health.
She has thirty years of teaching and professional experience, and has authored/
co-authored more than two hundred technical publications, including ten books and a dozen book chapters. Prior to becoming full-time at UdelaR, she worked for 19 years as a freelance Environmental and Sanitary Engineer.
Contents
Preface XIII
Section 1
Noise Pollution 1
Chapter 1 3
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel by Jānis Indulis Dundurs and Inka Janna Janssen
Chapter 2 21
Neighborhood Noise by Jiho Lee
Chapter 3 37
Attenuation of Environmental Noise through Digital Filtering by Juan Ríos and Celedonio Aguilar
Chapter 4 51
Innovative Approaches to Noise Reduction by Mia Suhanek and Sanja Grubesa
Chapter 5 75
Traffic Noise
by Sanja Grubesa and Mia Suhanek Section 2
Numerical and Experimental Application for Noise Reduction 97
Chapter 6 99
Noise Transmission Losses in Integrated Acoustic and Thermo-Fluid Insulation Panels
by Himanshu Dehra
Chapter 7 129
A New BEM for Modeling of Acoustic Wave Propagation in
Three-Temperature Nonlinear Generalized Magneto-Thermoelastic ISMFGA Structures Using Laser Ultrasonics
by Mohamed Abdelsabour Fahmy
Chapter 8 153
Underwater Ambient Noise
by Vijaya Baskar Veeriayan and Rajendran V.
Preface
Sound is an omnipresent agent in our society. Thus, so is noise. Occupational, social (or voluntary), and environmental (or passive) exposure to noise is a part of our lives. Research on noise pollution has inspired a wide set of researchers to study this interdisciplinary subject. Sources, causes, effects on people and other animals, control, regulations are some of the multiple aspects of the problem. This book offers current approaches to some of these topics: traffic noise, the noise of the neighborhood or underwater noise; occupational noise exposure in health emergency services; new approaches and materials to model and control noise problems. Acoustic materials are widely used by noise control engineers for NVH (Noise Vibration and Harshness) reduction in all fields of transportation. Noise has various effects on comfort, performance, and human health. For this reason, noise control plays an increasingly central role in the development of modern industrial and engineering applications.
Nowadays, the noise control problem excites and attracts the attention of a great number of scientists in different disciplines. Indeed, noise control has a wide vari- ety of applications in manufacturing, industrial operations, and consumer prod- ucts. The key to success for controlling noise inside interiors in the transportation field is to study and apply innovative materials with outstanding thermo-acoustic and mechanical properties. For this purpose, the book aims to present a collection of studies and applications in the field of innovative materials for interior acoustics in transport vehicles, for researchers and acoustic specialists.
The book is organized into 8 chapters written by specialists in the acoustic sector who use numerical and experimental techniques for noise reduction in the sur- rounding environment also through the study of innovative materials capable of reducing the effects on humans considered harmful to health.
The book means to supply the reader, both student and researcher or teacher, with extensive knowledge of the latest research results in innovative materials for acous- tics and new approaches to face such an old issue as noise pollution is. The editors are sincerely grateful to all the authors who agreed to share, with their professionalism and experience, their latest research results contributing to the success of this book.
Daniela Siano Istituto Motori CNR, Italy Alice Elizabeth Gonzalez Universidad de la Republica, Uruguay
Section 1
Noise Pollution
Chapter 1
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel
Jānis Indulis Dundurs and Inka Janna Janssen
Abstract
Every day, noise is a ubiquitous potential hazard to our body. Importance is already dedicated early in history and still continues by steady investigations in terms of protecting the personnel in loud environment. “Worldwide, 16% of hearing loss in adults is attributed to occupational noise.” Noise-induced hearing loss (NIHL) is a sensorineural hearing loss, explained by permanent threshold shift of hearing sensitivity. NIHL not only affects the auditory system but also has psychosocial effects and is proved to have interference with general health by sleep disturbances or cardiovascular symptoms. This study aims to detect and define the sound pressure levels that ambulance service workers are exposed to during their shifts in ambulance vehicle, especially with the focus on differences during signal and non-signal use and different speed levels and determining whether the noise has hazardous character. The collection of study data is composed of two parts.
The first part is the indication of noise level in the ambulance vehicle with the help of a sound level meter. The second part included a questionnaire that constituted 14 questions sent electronically. In total, 207 workers responded.
Keywords: Noise-induced hearing loss, emergency service personnel, ambulance vehicle
1. Introduction
Historically, the earliest descriptions about the danger of noise-induced hearing loss (NIHL) were described in 1713 by the Italian physician Bernardino Ramazzini (1633–1714). In his book “De Morbis Artificum” (Diseases of Workers), he firstly demonstrated the impact of hearing loss together in a relation to prolonged exposure to noise by his observations based on his examinations on coppersmith workers who were constantly exposed to noise and gradually suffered from hearing loss [1].
During the eighteenth century with onset of rapid industrialisation, the incidence of NIHL increased drastically and lead to the first ideas of preventive actions.
Almost 200 years later, the Hungarian biophysicist Georg von Békésy (1899–1972) analysed the travelling wave of sound in the cochlea, for which he received a Nobel Prize in 1961 and simultaneously set the cornerstone for the start of investigations of noise and hearing loss in relation to exposure time [2].
Noise and Environment
The origin of the noun “noise” is found in Latin language from the term
“nausea”, which later via detours through French language was introduced as
“noise” to the English language [3]. Both words have much more in common than suspected before.
Substantially, there is no difference between sound and noise. But enlighten- ing the differences more closely, sound refers to the sense of perception that usually occurs on voluntary basis and delights the listener as it is for example by listening to music. On the other hand, noise is defined as an unwanted sound that may cause displeasure, annoyance and pain or, referring back to its word origins, nausea.
Investigations have shown that continuous noise exposure has an enormous damaging impact not only on hearing but also on the general health status of the population.
Although preventable, NIHL is one of the most widespread irreversible occupational diseases worldwide and thus was declared as a serious occupational hazard [4].
Several studies gave evidence that noise creates physical and psychological stress, commonly presented as reduced assessment, sleep disturbances, cardiovas- cular dysfunction and mental health alteration [5, 6].
The protection of health and safety from hazards at work should be our all interest. Therefore, our research is aimed at evaluating the impact of occupational noise on hearing, general security of health, quality of life and productivity of those working in stressful environments shown at the example of emergency service working personnel, who give constantly their best to protect and save our health during emergency.
2. Literature review 2.1 Basics of acoustics
Noise can be described as rapid fluctuations in atmospheric pressure, which affects the human body as vibrations that are perceived by the human ear and finally can be classified as sound.
Sound propagates as a pressure wave and is able to travel through any elastic medium (e.g., air, water, wood, and metal).
Important units for measurements of noise attributes are hertz (Hz) and deci- bels (dB), and together with some basic knowledge of physics of waves, frequency, wavelength, amplitude, refraction, absorption and transmission, we are able to understand the behaviour of noise and can develop controls and preventions. When molecules start to move due to atmospheric pressure changes, the moving air mol- ecules pass their energy on to neighbouring molecules, which results in the spread of their energy over and over until an increasingly larger volume is created. This principle can be compared to the ripples when a stone is thrown into water. These described pressure changes are detected by the eardrum, which in return vibrates as response. In return, the vibrations are further transferred to the middle ear, which is constructed of three tiny bones facing towards the fluid-filled inner ear. The inner ear contains tiny inner and outer hair cells, which convert the vibrations into electrical nerve impulses that then are sent to the brain. Finally, the brain is then able to process these impulses into meaningful sounds [5, 7].
The perception of loudness of a sound is determined by two factors: sound pressure and frequency. The frequency (number of vibrations per second) is
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
related to “pitch”. The higher the frequency, the shaper the sound heard by the subject [7].
Important issues about noise perception are as follows: Sound pressure levels are measured in (dB). They describe the amplitude of the sound waves. They are related to the loudness of the sound. The A-weighted sound pressure levels are measured in dB(A). A-weighting considers the non-linear response to sound of the human ear, and also its non-homogeneous response to sounds of different frequencies and intensities. This level is determined by using a standardised weighting at different frequencies and then, summing logarithmically these sound pressure levels. The A-weighted sound pressure levels better represent the auditee’s perception of noise.
They are used for many applications, from community noise ordinances to occupa- tional noise exposure regulations.
2.1.1 Noise as a dangerous hazard
Every day, we are naturally exposed to loud, distracting and possibly hazardous noise. A common experience for everyone may be the example of continues ringing after a great concert or muffled sounds after working with loud tools (chainsaw, grass cutter, etc.).
Noise at prolonged exposure at 80 dB has unsafe effects to the auditory system but also to general health [5, 7, 8].
Studies proved that the risk for NIHL increases exponentially in noise-exposed population, who are exposed to noise level beyond 85 dB(A) for a prolonged time [9].
Table 1 shows critically how noise is correlated with health that is shown in three different stages of noise levels in dB(A).
At the example of “Conversation”, it can be nicely illustrated in what manner noise level has an impact on health.
A standard conversation is measured at approximately 50 dB(A), which at a pro- longed exposure may lead to mental reactions (e.g., low concentration and annoy- ance); at 80 dB(A), for communication, the voice needs to be elevated remarkably that interferes with health shown in physical reactions (e.g., hypertonus); and at 90 dB(A), communication is not possible anymore, which in return in long term is unbearable and triggers pain threshold.
2.1.2 Noise exposure and limit values
Determining the limit of noise exposure is crucial to take three components in consideration:
1. Worker (genetic predisposition)
2. Character of noise: sound pressure level and frequency 3. Duration of exposure
Generally, the potential and stage for hearing loss by noise are related to the workers’ duration of noise exposure and stage of noise loudness.
Halving acoustic energy can be done reducing sound pressure level by the 3 dB or halving the exposure time [10].
For better understanding, see the following examples. These noise exposures are the same:
Noise and Environment
The origin of the noun “noise” is found in Latin language from the term
“nausea”, which later via detours through French language was introduced as
“noise” to the English language [3]. Both words have much more in common than suspected before.
Substantially, there is no difference between sound and noise. But enlighten- ing the differences more closely, sound refers to the sense of perception that usually occurs on voluntary basis and delights the listener as it is for example by listening to music. On the other hand, noise is defined as an unwanted sound that may cause displeasure, annoyance and pain or, referring back to its word origins, nausea.
Investigations have shown that continuous noise exposure has an enormous damaging impact not only on hearing but also on the general health status of the population.
Although preventable, NIHL is one of the most widespread irreversible occupational diseases worldwide and thus was declared as a serious occupational hazard [4].
Several studies gave evidence that noise creates physical and psychological stress, commonly presented as reduced assessment, sleep disturbances, cardiovas- cular dysfunction and mental health alteration [5, 6].
The protection of health and safety from hazards at work should be our all interest. Therefore, our research is aimed at evaluating the impact of occupational noise on hearing, general security of health, quality of life and productivity of those working in stressful environments shown at the example of emergency service working personnel, who give constantly their best to protect and save our health during emergency.
2. Literature review 2.1 Basics of acoustics
Noise can be described as rapid fluctuations in atmospheric pressure, which affects the human body as vibrations that are perceived by the human ear and finally can be classified as sound.
Sound propagates as a pressure wave and is able to travel through any elastic medium (e.g., air, water, wood, and metal).
Important units for measurements of noise attributes are hertz (Hz) and deci- bels (dB), and together with some basic knowledge of physics of waves, frequency, wavelength, amplitude, refraction, absorption and transmission, we are able to understand the behaviour of noise and can develop controls and preventions. When molecules start to move due to atmospheric pressure changes, the moving air mol- ecules pass their energy on to neighbouring molecules, which results in the spread of their energy over and over until an increasingly larger volume is created. This principle can be compared to the ripples when a stone is thrown into water. These described pressure changes are detected by the eardrum, which in return vibrates as response. In return, the vibrations are further transferred to the middle ear, which is constructed of three tiny bones facing towards the fluid-filled inner ear. The inner ear contains tiny inner and outer hair cells, which convert the vibrations into electrical nerve impulses that then are sent to the brain. Finally, the brain is then able to process these impulses into meaningful sounds [5, 7].
The perception of loudness of a sound is determined by two factors: sound pressure and frequency. The frequency (number of vibrations per second) is
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
related to “pitch”. The higher the frequency, the shaper the sound heard by the subject [7].
Important issues about noise perception are as follows: Sound pressure levels are measured in (dB). They describe the amplitude of the sound waves. They are related to the loudness of the sound. The A-weighted sound pressure levels are measured in dB(A). A-weighting considers the non-linear response to sound of the human ear, and also its non-homogeneous response to sounds of different frequencies and intensities. This level is determined by using a standardised weighting at different frequencies and then, summing logarithmically these sound pressure levels. The A-weighted sound pressure levels better represent the auditee’s perception of noise.
They are used for many applications, from community noise ordinances to occupa- tional noise exposure regulations.
2.1.1 Noise as a dangerous hazard
Every day, we are naturally exposed to loud, distracting and possibly hazardous noise. A common experience for everyone may be the example of continues ringing after a great concert or muffled sounds after working with loud tools (chainsaw, grass cutter, etc.).
Noise at prolonged exposure at 80 dB has unsafe effects to the auditory system but also to general health [5, 7, 8].
Studies proved that the risk for NIHL increases exponentially in noise-exposed population, who are exposed to noise level beyond 85 dB(A) for a prolonged time [9].
Table 1 shows critically how noise is correlated with health that is shown in three different stages of noise levels in dB(A).
At the example of “Conversation”, it can be nicely illustrated in what manner noise level has an impact on health.
A standard conversation is measured at approximately 50 dB(A), which at a pro- longed exposure may lead to mental reactions (e.g., low concentration and annoy- ance); at 80 dB(A), for communication, the voice needs to be elevated remarkably that interferes with health shown in physical reactions (e.g., hypertonus); and at 90 dB(A), communication is not possible anymore, which in return in long term is unbearable and triggers pain threshold.
2.1.2 Noise exposure and limit values
Determining the limit of noise exposure is crucial to take three components in consideration:
1. Worker (genetic predisposition)
2. Character of noise: sound pressure level and frequency 3. Duration of exposure
Generally, the potential and stage for hearing loss by noise are related to the workers’ duration of noise exposure and stage of noise loudness.
Halving acoustic energy can be done reducing sound pressure level by the 3 dB or halving the exposure time [10].
For better understanding, see the following examples. These noise exposures are the same:
Noise and Environment
• 80 dB for 8 h
• 83 dB for 4 h
• 86 dB for 2 h
• 89 dB for 1 h
• 92 dB for 30 min
International standards recommend an “equivalent sound pressure level of 85 dB(A) at 8-h working day average as the exposure limit for occupational noise”
for preservation of the personnel’s hearing when working in a noisy environment.
However, in reality, it shows that this limit does not guarantee safety, especially for the hearing system of workers, since 80 dB(A) is already indicating harmful effects [11].
Therefore, Noise at Work Regulations recommend a “three action levels for occupational noise level” depending on equivalent noise level for 8-h working day (see Table 2).
2.2 Overview of hearing loss
Hearing loss can be categorised depending which parts of the hearing system are damaged. There are three basic types of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss [12].
Conductive hearing loss occurs due to damage of outer structures of the audi- tory system.
The sound waves are not properly conducting through the outer ear canal, the eardrum and ossicles of the middle ear. It is characterised by a reduction of sound level perception or the ability to hear weak sounds. Good treatment options are surgery or medication depending on issue.
Noise level and
body reaction Type of noise Sound pressure
levels in dB(A) Sound sense I30–65 dB(A)
Mental reaction
Fine ticking of a clock,
whispering 30 dB(A) Very quiet
Library, bedroom at night 40 dB(A) Pretty quiet
Conversation 50 dB(A) Normal
Quiet office 60 dB(A) Moderate to loud
II65–90 dB(A) Physical reaction
Shouting, car in 10 m distance 70 dB(A) Loud to very loud Street noise in heavy traffic 80 dB(A) Very loud III90–120 dB(A)
Hearing loss, ear pain
Loud factory hall 90 dB(A) Very loud
Car horns in 7 m distance 100 dB(A) Very loud to unbearable Full symphony orchestra 110 dB(A) Very loud to
unbearable Jet engine, live rock band 120 dB(A) Unbearable to painful
130 dB(A) Intolerable
Table 1.
Overview of noise level and impact on human body.
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
Causes of conductive hearing loss are as follows:
• Fluid in the middle ear
• Ear infection (otitis media or otitis externa)
• Poor eustachian tube function
• Trauma, e.g., perforated eardrum
• Obstacle such as cerumen, tumour or foreign body
Sensorineural hearing loss appears in case of damage to inner structures such as cochlea or to the nerve pathways from the inner ear to the brain.
Characteristically, it is described by the reduced ability to hear faint sounds.
Even when speech is loud enough to hear, it may still appear to be unclear or sound muffled. Unfortunately, there is no treatment option.
Examples:
• Ototoxic medication
• Genetic or hereditary
• Ageing
• Head trauma
• Exposure to loud noise 2.2.1 Noise-induced hearing loss
NIHL is one of the most common occupational illnesses, because it is often ignored since there are no visible effects or pain sensation in early stages.
Factors that especially predispose one to NIHL are found in high-frequency noise exposure, which is known to be much more harmful than low-frequency noise, and also continuous stimuli are more damaging than interrupted stimuli.
NIHL starts with a temporary threshold shift (TTS). Physiologically explained, while the ear is exposed to the noise, there originates a release of ATP from stria cochlearis, which provides the necessary energy for the function of the hair cells.
In case of prolonged elevated noise exposure, a mismatch occurs between energy supply and consumption, as the ATP needs to reach the hair cells by diffusion. The hair cells get tired due to energy depletion and result to be less sensitive. This leads
Action level LAeq8h
First action level (minimum) provide protection 80 dB(A)
Second action level mandatory protection 85 dB(A)
Maximum exposure limit value 87 dB(A)
Table 2.
Three action levels for occupational noise level.
Noise and Environment
• 80 dB for 8 h
• 83 dB for 4 h
• 86 dB for 2 h
• 89 dB for 1 h
• 92 dB for 30 min
International standards recommend an “equivalent sound pressure level of 85 dB(A) at 8-h working day average as the exposure limit for occupational noise”
for preservation of the personnel’s hearing when working in a noisy environment.
However, in reality, it shows that this limit does not guarantee safety, especially for the hearing system of workers, since 80 dB(A) is already indicating harmful effects [11].
Therefore, Noise at Work Regulations recommend a “three action levels for occupational noise level” depending on equivalent noise level for 8-h working day (see Table 2).
2.2 Overview of hearing loss
Hearing loss can be categorised depending which parts of the hearing system are damaged. There are three basic types of hearing loss: conductive hearing loss, sensorineural hearing loss, and mixed hearing loss [12].
Conductive hearing loss occurs due to damage of outer structures of the audi- tory system.
The sound waves are not properly conducting through the outer ear canal, the eardrum and ossicles of the middle ear. It is characterised by a reduction of sound level perception or the ability to hear weak sounds. Good treatment options are surgery or medication depending on issue.
Noise level and
body reaction Type of noise Sound pressure
levels in dB(A) Sound sense I30–65 dB(A)
Mental reaction
Fine ticking of a clock,
whispering 30 dB(A) Very quiet
Library, bedroom at night 40 dB(A) Pretty quiet
Conversation 50 dB(A) Normal
Quiet office 60 dB(A) Moderate to loud
II65–90 dB(A) Physical reaction
Shouting, car in 10 m distance 70 dB(A) Loud to very loud Street noise in heavy traffic 80 dB(A) Very loud III90–120 dB(A)
Hearing loss, ear pain
Loud factory hall 90 dB(A) Very loud
Car horns in 7 m distance 100 dB(A) Very loud to unbearable Full symphony orchestra 110 dB(A) Very loud to
unbearable Jet engine, live rock band 120 dB(A) Unbearable to painful
130 dB(A) Intolerable
Table 1.
Overview of noise level and impact on human body.
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
Causes of conductive hearing loss are as follows:
• Fluid in the middle ear
• Ear infection (otitis media or otitis externa)
• Poor eustachian tube function
• Trauma, e.g., perforated eardrum
• Obstacle such as cerumen, tumour or foreign body
Sensorineural hearing loss appears in case of damage to inner structures such as cochlea or to the nerve pathways from the inner ear to the brain.
Characteristically, it is described by the reduced ability to hear faint sounds.
Even when speech is loud enough to hear, it may still appear to be unclear or sound muffled. Unfortunately, there is no treatment option.
Examples:
• Ototoxic medication
• Genetic or hereditary
• Ageing
• Head trauma
• Exposure to loud noise 2.2.1 Noise-induced hearing loss
NIHL is one of the most common occupational illnesses, because it is often ignored since there are no visible effects or pain sensation in early stages.
Factors that especially predispose one to NIHL are found in high-frequency noise exposure, which is known to be much more harmful than low-frequency noise, and also continuous stimuli are more damaging than interrupted stimuli.
NIHL starts with a temporary threshold shift (TTS). Physiologically explained, while the ear is exposed to the noise, there originates a release of ATP from stria cochlearis, which provides the necessary energy for the function of the hair cells.
In case of prolonged elevated noise exposure, a mismatch occurs between energy supply and consumption, as the ATP needs to reach the hair cells by diffusion. The hair cells get tired due to energy depletion and result to be less sensitive. This leads
Action level LAeq8h
First action level (minimum) provide protection 80 dB(A)
Second action level mandatory protection 85 dB(A)
Maximum exposure limit value 87 dB(A)
Table 2.
Three action levels for occupational noise level.
Noise and Environment
to a shift in hearing threshold but has still potential to recover completely when the harmful stimulus is removed [13].
If the exposure to the harmful noise still continues, the cellular integrity of the hair cells of the Corti organ disrupts gradually and ultimately the nerve fibres that innervate the hair cells will disappear, thus resulting in permanent threshold shift (PTS), and henceforth, irreversible hearing loss at higher frequencies will be noted. In most cases, it is described affecting both ears symmetrically [14].
NIHL can be classified into four stages: mild, moderate, severe and profound [15].
1. Mild NIHL is a high-frequency hearing loss of sounds between 20 and 40 dB.
2. Moderate NIHL, between 40 and 60 dB.
3. Severe NIHL, between 60 and 80 dB.
4. Profound NIHL, greater than 80 dB.
Limitations in hearing are evident when listening to high frequencies. First noticed problems are trouble understanding speech during present background noise. NIHL progresses gradually, and people have difficulty understanding high- pitched voices (e.g., women and children) even in quiet conversational situations, whereas conversation on the telephone is generally unaffected.
TTS slowly progresses to PTS, post exposure tinnitus, and TTS serves as warn- ing signs of impending permanent NIHL [14].
2.2.2 Audiogram
Hearing loss is detectable by performing an audiogram and is presented as a graph that shows the weakest sounds a person can hear at different frequencies.
It can be used to detect the concrete severity of sensorineural hearing loss or for check-up reasons.
For TTS, there is a chance that the shift regresses again after the noise is removed.
Therefore, the sound pressure level during the recovery period is kept below 70 dB(A) and a recovery time of at least 10 h.
In case the recovery period is not respected, an accumulation of the individual TTS may occur and leads to PTS, which can be detected in the audiogram (see Figure 1).
NIHL is typically shown with selective loss of hearing at around 4000 Hz, which is apparent in the audiogram as a notch-like depression.
If exposure to harming noise is continued, the notch gradually deepens and widens. It can also take over to the middle frequencies. In very severe cases, even the lower frequencies may eventually become involved [5].
2.3 Consequences of NIHL
Consequences of NIHL may severely interfere with both social and occupational environment. NIHL as a reason for limited communication ability with co-workers and family may develop anxiety, irritability and decreased self-esteem resulting in loss of productivity and, eventually, social isolation.
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
In terms of safety, NIHL often runs together with a reduced ability of assessment and to monitor work environment such as warning signals or equipment sounds and immensely increase the danger of injuries.
2.3.1 Health risks
Noise creates physical and psychological stress that can interfere with health leading to extra aural health risks. Common early symptoms can be found psycho- socially as sleep disturbances, concentration difficulties and clumsiness.
Depending on the extent of sound pressure level, it can influence the vegetative system by a shift in favour towards the sympathetic nervous system. Examples are tachycardia, hypertonia, tachypnoea, increased adrenal secretion of stress hormones such as cortisol and decrease in gastric secretion for protection of gastric mucosa. In the long term, these symptoms have potential to interfere severely with health [16].
3. Methods and materials 3.1 Study design
The data were collected through a retrospective cohort study using a question- naire with a total sample size of 207 workers from two main emergency ambulance service centres located in Riga, Latvia, and Aurich, Germany.
Figure 1.
Audiogram characterising early NIHL.
Noise and Environment
to a shift in hearing threshold but has still potential to recover completely when the harmful stimulus is removed [13].
If the exposure to the harmful noise still continues, the cellular integrity of the hair cells of the Corti organ disrupts gradually and ultimately the nerve fibres that innervate the hair cells will disappear, thus resulting in permanent threshold shift (PTS), and henceforth, irreversible hearing loss at higher frequencies will be noted. In most cases, it is described affecting both ears symmetrically [14].
NIHL can be classified into four stages: mild, moderate, severe and profound [15].
1. Mild NIHL is a high-frequency hearing loss of sounds between 20 and 40 dB.
2. Moderate NIHL, between 40 and 60 dB.
3. Severe NIHL, between 60 and 80 dB.
4. Profound NIHL, greater than 80 dB.
Limitations in hearing are evident when listening to high frequencies. First noticed problems are trouble understanding speech during present background noise. NIHL progresses gradually, and people have difficulty understanding high- pitched voices (e.g., women and children) even in quiet conversational situations, whereas conversation on the telephone is generally unaffected.
TTS slowly progresses to PTS, post exposure tinnitus, and TTS serves as warn- ing signs of impending permanent NIHL [14].
2.2.2 Audiogram
Hearing loss is detectable by performing an audiogram and is presented as a graph that shows the weakest sounds a person can hear at different frequencies.
It can be used to detect the concrete severity of sensorineural hearing loss or for check-up reasons.
For TTS, there is a chance that the shift regresses again after the noise is removed.
Therefore, the sound pressure level during the recovery period is kept below 70 dB(A) and a recovery time of at least 10 h.
In case the recovery period is not respected, an accumulation of the individual TTS may occur and leads to PTS, which can be detected in the audiogram (see Figure 1).
NIHL is typically shown with selective loss of hearing at around 4000 Hz, which is apparent in the audiogram as a notch-like depression.
If exposure to harming noise is continued, the notch gradually deepens and widens. It can also take over to the middle frequencies. In very severe cases, even the lower frequencies may eventually become involved [5].
2.3 Consequences of NIHL
Consequences of NIHL may severely interfere with both social and occupational environment. NIHL as a reason for limited communication ability with co-workers and family may develop anxiety, irritability and decreased self-esteem resulting in loss of productivity and, eventually, social isolation.
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
In terms of safety, NIHL often runs together with a reduced ability of assessment and to monitor work environment such as warning signals or equipment sounds and immensely increase the danger of injuries.
2.3.1 Health risks
Noise creates physical and psychological stress that can interfere with health leading to extra aural health risks. Common early symptoms can be found psycho- socially as sleep disturbances, concentration difficulties and clumsiness.
Depending on the extent of sound pressure level, it can influence the vegetative system by a shift in favour towards the sympathetic nervous system. Examples are tachycardia, hypertonia, tachypnoea, increased adrenal secretion of stress hormones such as cortisol and decrease in gastric secretion for protection of gastric mucosa. In the long term, these symptoms have potential to interfere severely with health [16].
3. Methods and materials 3.1 Study design
The data were collected through a retrospective cohort study using a question- naire with a total sample size of 207 workers from two main emergency ambulance service centres located in Riga, Latvia, and Aurich, Germany.
Figure 1.
Audiogram characterising early NIHL.
Noise and Environment
Additionally, the noise level was detected by measurements with a sound level meter.
3.2 Description of data collection Materials of use:
1. Questionnaire (14 questions) 2. Sound level meter
The collection of data is divided into two parts.
The first part includes the collection of basic personal and working information via a questionnaire of 14 questions. Hundred and five Latvian and hundred and two German emergency service workers responded to the questionnaire. The question- naire was shared as electronic survey at http://www.visidati.lv and also distributed as printed paper to the different working stations. The collection of personnel information started in January 2016 and ended in May 2016.
The research data were collected and statistically processed in Microsoft Office Excel 2010 and SPSS 22.0.
The second part refers to the measurement of noise level by use of a sound level meter reviewing non-signal and signal noise exposures during 12-h shifts and by this giving the basis to analyse the average noise level that an emergency service personnel is presented to.
The collection of measurement started in January 2016 and ended in February 2016.
Digital sound level meter model LUTRON SL-4013 conforms to IEC 651 Type 2 with 0’. Noise was measured using a standard microphone head that was placed in the front passenger compartment of an ambulance during emergency driving. The equipment was programmed to collect data in fast mode, using the weighting curve
“A”. Also, a protective foam in the microphone in order to minimise the other noise effects was used.
The measurements were recorded during 20 emergency trips with a duration range from 10 to 15 min. These measurements were performed in different days, periods and shifts. The noise levels were carefully recorded at different velocities under the following conditions:
• Asphalt street and good surface conditions of the street
• Measuring device placed in the centre of the cabin at level of the ears of workers
• Taking measured number at stable driving of 50, 70 and 100 km/h
• Mostly free field as surrounding (no high density of high houses)
• No talking, no funk communication
• Radio turned off
• Windows closed
• No rain, calm wind
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
The ambulance car is analysed in terms of technical specification and physical dimensions.
For proper comparison of the ambulance service in Germany and Latvia, we chose similar cars in model and age.
Both countries use the Mercedes-Benz, Sprinter 315, CDI model, 4-door, manual and manufacturing year 2010 (Riga, Latvia) and a similar model from year 2012 (Aurich, Germany) This model is a standard Sprinter with high ceilings. The front cabin design layout constituted likewise.
The sirens are located bilaterally on the roof and front spoiler of the ambulance car. The type of sirens and frequency for Latvia and Germany differ especially in frequency of sound melody. Germany is using sirens of type “Martin-Horn 2298 GM”
DIN 14610 EC with a 4′ membrane-bell and sound pressure level of 125 dB(A) at a distance of 1 m.
In Latvia, there is no standardised sound melody throughout a signal trip.
During signal trips, the driver can choose manually between different frequencies.
4. Research results
4.1 Sound level meter measurements
The average sound levels based on the measurements performed during numer- ous emergency trips are as shown in Table 3.
In Germany, the minimum noise level is measured at 50 km/h without signal use with 63.5 dB(A) and the maximum is measured at 100 km/h with signal use with 84.8 dB(A).
In comparison, in Latvia, the minimum is measured at 50 km/h without signal use with 67.3 dB(A) and the maximum is measured at 100 km/h with signal use with 90.7 dB(A).
For both countries, it is noticeable that the noise level during signal use is enormously elevated than during trips without signal use. Comparing the Latvian with German emergency cars, non-signal trips are measured with a higher average noise level with an average difference of 5.2 dB(A) and during signal use the noise level in Latvian emergency cars is also higher by a difference average of 2.4 dB(A).
This means, the Latvian emergency personnel is exposed to an overall higher noise level during emergency trips than German emergency personnel.
4.2 Questionnaire
The research included in total count 207 emergency workers from different emergency service centres. Hundred and two German and hundred and five
Germany Latvia
Without signal With signal Without signal With signal
Average 66.5 84.7 71.9 86.6
50 km/h 63.5 84.4 67.2 83.3
70 km/h 65.2 84.8 72.4 85.9
100 km/h 71.4 84.8 76.1 90.7
Table 3.
Measured sound pressure level in dB(A) according to speed and considering all data together, for Germany and Latvia.
Noise and Environment
Additionally, the noise level was detected by measurements with a sound level meter.
3.2 Description of data collection Materials of use:
1. Questionnaire (14 questions) 2. Sound level meter
The collection of data is divided into two parts.
The first part includes the collection of basic personal and working information via a questionnaire of 14 questions. Hundred and five Latvian and hundred and two German emergency service workers responded to the questionnaire. The question- naire was shared as electronic survey at http://www.visidati.lv and also distributed as printed paper to the different working stations. The collection of personnel information started in January 2016 and ended in May 2016.
The research data were collected and statistically processed in Microsoft Office Excel 2010 and SPSS 22.0.
The second part refers to the measurement of noise level by use of a sound level meter reviewing non-signal and signal noise exposures during 12-h shifts and by this giving the basis to analyse the average noise level that an emergency service personnel is presented to.
The collection of measurement started in January 2016 and ended in February 2016.
Digital sound level meter model LUTRON SL-4013 conforms to IEC 651 Type 2 with 0’. Noise was measured using a standard microphone head that was placed in the front passenger compartment of an ambulance during emergency driving. The equipment was programmed to collect data in fast mode, using the weighting curve
“A”. Also, a protective foam in the microphone in order to minimise the other noise effects was used.
The measurements were recorded during 20 emergency trips with a duration range from 10 to 15 min. These measurements were performed in different days, periods and shifts. The noise levels were carefully recorded at different velocities under the following conditions:
• Asphalt street and good surface conditions of the street
• Measuring device placed in the centre of the cabin at level of the ears of workers
• Taking measured number at stable driving of 50, 70 and 100 km/h
• Mostly free field as surrounding (no high density of high houses)
• No talking, no funk communication
• Radio turned off
• Windows closed
• No rain, calm wind
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
The ambulance car is analysed in terms of technical specification and physical dimensions.
For proper comparison of the ambulance service in Germany and Latvia, we chose similar cars in model and age.
Both countries use the Mercedes-Benz, Sprinter 315, CDI model, 4-door, manual and manufacturing year 2010 (Riga, Latvia) and a similar model from year 2012 (Aurich, Germany) This model is a standard Sprinter with high ceilings. The front cabin design layout constituted likewise.
The sirens are located bilaterally on the roof and front spoiler of the ambulance car. The type of sirens and frequency for Latvia and Germany differ especially in frequency of sound melody. Germany is using sirens of type “Martin-Horn 2298 GM”
DIN 14610 EC with a 4′ membrane-bell and sound pressure level of 125 dB(A) at a distance of 1 m.
In Latvia, there is no standardised sound melody throughout a signal trip.
During signal trips, the driver can choose manually between different frequencies.
4. Research results
4.1 Sound level meter measurements
The average sound levels based on the measurements performed during numer- ous emergency trips are as shown in Table 3.
In Germany, the minimum noise level is measured at 50 km/h without signal use with 63.5 dB(A) and the maximum is measured at 100 km/h with signal use with 84.8 dB(A).
In comparison, in Latvia, the minimum is measured at 50 km/h without signal use with 67.3 dB(A) and the maximum is measured at 100 km/h with signal use with 90.7 dB(A).
For both countries, it is noticeable that the noise level during signal use is enormously elevated than during trips without signal use. Comparing the Latvian with German emergency cars, non-signal trips are measured with a higher average noise level with an average difference of 5.2 dB(A) and during signal use the noise level in Latvian emergency cars is also higher by a difference average of 2.4 dB(A).
This means, the Latvian emergency personnel is exposed to an overall higher noise level during emergency trips than German emergency personnel.
4.2 Questionnaire
The research included in total count 207 emergency workers from different emergency service centres. Hundred and two German and hundred and five
Germany Latvia
Without signal With signal Without signal With signal
Average 66.5 84.7 71.9 86.6
50 km/h 63.5 84.4 67.2 83.3
70 km/h 65.2 84.8 72.4 85.9
100 km/h 71.4 84.8 76.1 90.7
Table 3.
Measured sound pressure level in dB(A) according to speed and considering all data together, for Germany and Latvia.
Noise and Environment
Figure 2.
The percentage of survey population by gender.
Latvian emergency workers answered fourteen questions in an electronic form at http://www.visidati.lv or in printed version.
4.2.1 Population characteristics
In total, the respondents are defined by 116 (56%) men and 91 (44%) women aged between 18 and 65 years.
In Germany, the majority of personnel is formed by men (35%), while in Latvia, the majority is dominated by female workers (30%) (see Figure 2).
The age distribution shows that the Latvian emergency personnel in gen- eral are composed of a rather young team in the age range of 18–30 years
(18–25 years = 57.1%, 26–30 years = 30.5%), and in return, the German personnel show a wider range of age distribution, which majorly is observed to be between 18 and 40 years (18–25 years = 46.1%, 26–30 years = 22.5%, 31–40 years = 16.7%).
Consequently, the emergency workers in Germany are older compared to the Latvian emergency workers (see Figure 3).
Relating the personnel’s age and years of employment, a correlation is apparent.
The vast majority of the young Latvian workers have been working for 1–5 years (84.8%) and then an abrupt decrease of employment time by approximately 80%
is seen, while the investigated German ambulance service also has its peak employ- ment time at 1–5 years (54.9%) but then gradually decreases by 50% (see Figure 4).
According to the amount of shifts per week and the density of emergency occurrence, both countries have four shifts of 12 h during a 7-day working week and parallels are seen for the average amount of trips that are set at approximately six non-signal and five signal trips for both countries.
Evaluating the amount of hours the worker is exposed to noise during trips, the German ambulance service personnel are approximately 1.5 h (63 min) longer exposed to noises from signal and 0.71 h (43 min) longer exposed to non-signal noises during a 12-h shift. Comparing both countries for their total emergency
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
Figure 3.
The distribution in absolute numbers of survey population by age, Latvia and Germany in comparison.
Figure 4.
The distribution in absolute numbers of survey population by years of employment, Latvia and Germany in comparison.
Noise and Environment
Figure 2.
The percentage of survey population by gender.
Latvian emergency workers answered fourteen questions in an electronic form at http://www.visidati.lv or in printed version.
4.2.1 Population characteristics
In total, the respondents are defined by 116 (56%) men and 91 (44%) women aged between 18 and 65 years.
In Germany, the majority of personnel is formed by men (35%), while in Latvia, the majority is dominated by female workers (30%) (see Figure 2).
The age distribution shows that the Latvian emergency personnel in gen- eral are composed of a rather young team in the age range of 18–30 years
(18–25 years = 57.1%, 26–30 years = 30.5%), and in return, the German personnel show a wider range of age distribution, which majorly is observed to be between 18 and 40 years (18–25 years = 46.1%, 26–30 years = 22.5%, 31–40 years = 16.7%).
Consequently, the emergency workers in Germany are older compared to the Latvian emergency workers (see Figure 3).
Relating the personnel’s age and years of employment, a correlation is apparent.
The vast majority of the young Latvian workers have been working for 1–5 years (84.8%) and then an abrupt decrease of employment time by approximately 80%
is seen, while the investigated German ambulance service also has its peak employ- ment time at 1–5 years (54.9%) but then gradually decreases by 50% (see Figure 4).
According to the amount of shifts per week and the density of emergency occurrence, both countries have four shifts of 12 h during a 7-day working week and parallels are seen for the average amount of trips that are set at approximately six non-signal and five signal trips for both countries.
Evaluating the amount of hours the worker is exposed to noise during trips, the German ambulance service personnel are approximately 1.5 h (63 min) longer exposed to noises from signal and 0.71 h (43 min) longer exposed to non-signal noises during a 12-h shift. Comparing both countries for their total emergency
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
Figure 3.
The distribution in absolute numbers of survey population by age, Latvia and Germany in comparison.
Figure 4.
The distribution in absolute numbers of survey population by years of employment, Latvia and Germany in comparison.
Noise and Environment
Figure 5.
Time of exposure of the survey population to signal and non-signal trips during a 12-h shift. *Others include the time during the 12-h shift outside the emergency car.
trip-related noise exposure during a 12-h shift, German personnel are in total 68%
exposed to noise and Latvian personnel in total 53% (see Figure 5).
The time that the worker is not sitting in the car and presented to the evaluated noise is categorised as “other” in Figure 5, which stands for the time, e.g., in the hospital, patient house or guardhouse. It is impossible to measure these noise levels;
nonetheless, it should be taken into consideration, since presentation to noise is ubiquitous and affecting the body.
4.2.2 Symptom prevalence
In the questionnaire, respondents were allowed to choose more than one symp- tom and indeed, most respondents indicated more than one symptom. In compari- son, Germans assigned 1–2 fitting symptoms and Latvians choose 2–3 (see Figure 6).
For both countries, a common pattern of complaints and also highest incidences were found in following two symptoms: difficulties of understanding during back- ground noises (Germany 30.2%, N = 42 and Latvia 26.6%, N = 46) and tinnitus (Germany 38.8%, N = 52 and Latvia 23.8%, N = 41).
Other similarities but with lower frequency are given for hyperacusis (Germany 6%, N = 6 and Latvia 5.8%, N = 10), pain or pressure in the ear (Germany 13.4%, N = 18 and Latvia 13.4%, N = 23) and difficulties understanding speech, particu- larly women and children (Germany 7.9%, N = 11 and Latvia 10.4%, N = 18).
Comparing main differences, Latvian emergency workers show a much higher incidence of symptoms such as vertigo (23.8%, N = 41), changes in sound per- ception (7.5%, N = 13), difficulties in determination of sound direction (5.8%, N = 10) and difficulties using the phone due to poor understanding of the partner (13.3%, N = 23).
German emergency personnel showed higher prevalence only for difficulties understanding electronic audio devices such as TV and radio and thus the need to increase the volume (20.9%, N = 28).
Concluding, Latvian emergency personnel clearly dominate in 8 from 10 audi- tory symptoms with higher absolute number.
For a closer accurate evaluation risks for NIHL, also an average noise exposure during free time was requested giving a defined range from 1 (low noise exposure) to 10 (high noise exposure). Both indicated an average free time exposure to noise at 5.
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
4.2.3 Statistical data
Statistical investigations for relations according to the study showed that there is no significant relation between countries, age, gender or length of employment towards symptoms (p > 0.05) and thus cannot be attributed to the general population.
5. Discussion
When persons with normal hearing are exposed to high noise levels over a prolonged period of time and by this reaching or exceeding the limit of permissible noise level exposure equivalent of 85 dB(A) during 8 h, a shift of hearing threshold may result. Under a threshold shift is meant an average deterioration of hearing of 10 dB(A) or more in the frequency ranges of 2000, 3000 and 4000 Hz in both ears, defined by Occupational Safety and Health Act (OSHA).
Figure 6.
Prevalence of chronic hearing symptoms for each country of the survey population in absolute number, Germany and Latvia in comparison.
Noise and Environment
Figure 5.
Time of exposure of the survey population to signal and non-signal trips during a 12-h shift. *Others include the time during the 12-h shift outside the emergency car.
trip-related noise exposure during a 12-h shift, German personnel are in total 68%
exposed to noise and Latvian personnel in total 53% (see Figure 5).
The time that the worker is not sitting in the car and presented to the evaluated noise is categorised as “other” in Figure 5, which stands for the time, e.g., in the hospital, patient house or guardhouse. It is impossible to measure these noise levels;
nonetheless, it should be taken into consideration, since presentation to noise is ubiquitous and affecting the body.
4.2.2 Symptom prevalence
In the questionnaire, respondents were allowed to choose more than one symp- tom and indeed, most respondents indicated more than one symptom. In compari- son, Germans assigned 1–2 fitting symptoms and Latvians choose 2–3 (see Figure 6).
For both countries, a common pattern of complaints and also highest incidences were found in following two symptoms: difficulties of understanding during back- ground noises (Germany 30.2%, N = 42 and Latvia 26.6%, N = 46) and tinnitus (Germany 38.8%, N = 52 and Latvia 23.8%, N = 41).
Other similarities but with lower frequency are given for hyperacusis (Germany 6%, N = 6 and Latvia 5.8%, N = 10), pain or pressure in the ear (Germany 13.4%, N = 18 and Latvia 13.4%, N = 23) and difficulties understanding speech, particu- larly women and children (Germany 7.9%, N = 11 and Latvia 10.4%, N = 18).
Comparing main differences, Latvian emergency workers show a much higher incidence of symptoms such as vertigo (23.8%, N = 41), changes in sound per- ception (7.5%, N = 13), difficulties in determination of sound direction (5.8%, N = 10) and difficulties using the phone due to poor understanding of the partner (13.3%, N = 23).
German emergency personnel showed higher prevalence only for difficulties understanding electronic audio devices such as TV and radio and thus the need to increase the volume (20.9%, N = 28).
Concluding, Latvian emergency personnel clearly dominate in 8 from 10 audi- tory symptoms with higher absolute number.
For a closer accurate evaluation risks for NIHL, also an average noise exposure during free time was requested giving a defined range from 1 (low noise exposure) to 10 (high noise exposure). Both indicated an average free time exposure to noise at 5.
Influence of Noise in Ambulance Vehicles on Emergency Service Personnel DOI: http://dx.doi.org/10.5772/intechopen.91898
4.2.3 Statistical data
Statistical investigations for relations according to the study showed that there is no significant relation between countries, age, gender or length of employment towards symptoms (p > 0.05) and thus cannot be attributed to the general population.
5. Discussion
When persons with normal hearing are exposed to high noise levels over a prolonged period of time and by this reaching or exceeding the limit of permissible noise level exposure equivalent of 85 dB(A) during 8 h, a shift of hearing threshold may result. Under a threshold shift is meant an average deterioration of hearing of 10 dB(A) or more in the frequency ranges of 2000, 3000 and 4000 Hz in both ears, defined by Occupational Safety and Health Act (OSHA).
Figure 6.
Prevalence of chronic hearing symptoms for each country of the survey population in absolute number, Germany and Latvia in comparison.
